Spreading of particulate matter

ABSTRACT

A process and apparatus for continuous uniform distribution of particulate matter onto a substrate. The apparatus comprises a hollow cylinder having a slot extending along its effective length, and a rotatable member located coaxially within the cylinder, the member having a plurality of vanes, each as long at least as the slot, the outer edges of the vanes being adjacent but not touching the inner wall of the cylinder and the vanes having a radially measured dimension less than the radius of the cylinder to define a central channel within the member. When particulate matter is supplied and suspended in a turbulent stream of gaseous fluid to the central channel, and the member is rotated, the particulate matter issues from the slot in a uniform distribution.

United States Patent 1191 Fox et a1.

1 1 Nov. 11, 1975 1 SPREADING OF PARTICULATE MATTER [75] Inventors: JohnCuthbert Fox; Martin Richard Winterbottom; Michael Frank Culpin, all ofPontypool, England 221 Filed: Aug. 24, 1972 211 App]. No.: 283,289

[30] Foreign Application Priority Data Wilhelm 1 18/308 3.230.105 1/1966Spraul et a1 1124/3014 3.299.853 1/1967 Whitaere 118/312 3,426,7292/1969 Hawkins 118/312 3.678.894 7/1972 Walsh 118/308 PrimurE.\'un1t'm'/'Mervin Stein Assistant Iitaminer-D0uglas Salser Attorney,Agent, or Fir/21-Cushman. Darby & Cushman [57] ABSTRACT A process andapparatus for continuous uniform distribution of particulate matter ontoa substrate.

The apparatus comprises a hollow cylinder having a slot extending alongits effective length, and a rotatable member -located coaxially withinthe cylinder, the member having a plurality of vanes, each as long atleast as the slot, the outer edges of the vanes being adjacent but nottouching the inner wall of the cylinder and the vanes having a radiallymeasured dimension less than the radius of the cylinder to define acentral channel Within the member. When particulate matter is suppliedand suspended in a turbulent stream of gaseous fluid to the centralchannel, and the member is rotated, the particulate matter issues fromthe slot in a uniform distribution.

13 Claims, 4 Drawing Figures US. Patent Nov. 11, 1975 Sheet 1 of23,918,399

US. Patent Nov.11, 1975 Sheet20f2 3,918,399

SPREADING OF PARTI C ULATE MATTER The invention relates to improvementsin spreading small particles of material in a uniform manner onto asurface. More particularly the invention relates to a method, andapparatus, for spreading flock fibres uniformly onto a. substrate.

lt has previously been proposed to apply flock fibres onto a substrateto which adhesive has been applied by spreading an excess of said flockfibres onto the substrate and thereafter removing the excess flockfibres which have not adhered to the substrate, by a vacuumingtechnique. lt has also been proposed to direct flock fibres onto asubstrate by means of an electrostatic field. The former method requiresan initial substantially uniform distribution of flock fibres followedby costly vacuuming and, optionally, recirculation devices for copingwith the excess flock applied to the substrate. The final weight offlock adhered to the substrate using this method is determined by thequantity and distribution of adhesive. The second method requires thegeneration and maintenance of a uniform electrostatic field and producesa product in which the flock fibres are aligned with their long axes atleast substantially perpendicular to the plane of the substrate. Whenthe object of flocking is principally to increase the opacity of thesubstrate, then such an arrangement of flock fibres is neither necessarynor desirable.

' We have now invented an improved method and apparatusfor distributingflock fibres in a uniform manner onto a substrate which requires neitherthe use of an excess quantity of flock, nor the use of an electrostaticfield.

Accordingly the invention provides in one of its aspects a process forthe continuous uniform distribution of particulate matter onto asubstrate advancing at a constant rate, comprising continuously forminga suspension of said particulate matter in a turbulent stream of gaseousfluid, and directing said suspension whilst maintaining turbulence inthe gaseous fluid onto the said substrate at a constant mass flow rate.

Generally the gaseous fluid will be air.

The apparatus for performing the above process comprises a hollowcylinder provided with a slot extending along its effective length and amember located coaxially within the cylinder and rotatable about itslengthwise axis comprising support means'extendin'g beyond the ends ofsaid hollow cylinder and having mounted therebetween a plurality ofvanes disposedwithin the said hollow cylinder, each vane extending alongthe entire effective length at least of said hollow cylinder, the outeredges of said vanes being adjacent but not touching the inner wall ofsaid cylinder and said vanes having radially measured dimensions lessthan the internal radius of the hollow cylinder to define a central,cylindrical channel within the said member means for supplyingparticulate matter suspended in a turbulent stream of gaseous fluid at aconstant rate to the said channel defined within said member, means foraxially rotating said member at a uniform rate and means for advancing asubstrate perpendicular to said slot in said hollow cylinder.

The apparatus is capable of uniformly distributing small quantities ofparticulate material over a large area. For example, we have distributedas little as 0.5 g of a-cellulos'e flock fibres uniformly over 1 squaremetre. The apparatus is equally capable, however, of metering anddistributing uniformly much larger quantities of particulate matter athigh rates.

By effective length" of the first member we mean the width over which itis desired to deposit particulate matter. Thus the slot need not extendacross the whole width of the first member. However, it is desirablethat the length of the vanes should be at least as long as the slot.

It is only necessary that the vanes of the second member be mounted tosupport means at their desirable although frequently it will provedisirable to provide a number of strengthening and bracing means atspaced intervals along the length of the vanes. The bracing meansconnect adjacent vanes and thereby serve to stiffen up the secondmember. Care must be taken, however, to ensure that the presence of thebracing means does not interfere with the uniform deposition ofparticulate matter and, therefore, we prefer to use the minimum ofbracing means necessary to maintain the second member stable.

Advantage may lie in avoiding positioning the bracing means in planesperpendicular to the axis of the apparatus, since the presence of thebracing means may produce irregular distribution of the particulatematter on the substrate material which will be apparent aslongitudinally extending stripes. Alternatively We find that a uniformdistribution may be obtained if a large number of bracing meanspositioned perpendicularly to the axis of the apparatus are employed,for example, if the bracing means are spaced at intervals of between2and 8 cm apart along the length of the second member. The latterarrangement is preferred for reasons of ease of manufacture. Theclearance between the ends of the vanes of the second member and theinner walls of the enclosing first member should be as small as ispracticable. The number of vanes is an important factor in achievinguniform flock deposition and should not be less than 6, preferably notless than 16. Preferably the vanes are symmetrically disposed around theaxis.

If desired the stability of the second member can be further increasedby means of an axially situated shaft with the hollow channel, whichshaft serves to link the vane support means.

We have observed that} the distribution of flock fibres onto a substrateimproves as the number of vanes passing the slot increases. S-uchimprovement can obviously be achieved either by using a second memberwith a relatively large number of vanes, at a relatively low speed ofrevolution or, alternatively, a small number of vanes at high speeds ofrevolution.

The actual design of the vanes may take a number of forms. For examplethe vanes may be of plane rectanvshaped, with, for example, thethickness of the crosssection greater at the vane tip than towards thecentre of the vane assembly. Again, the vanes may be curved in theplanes perpendicular and/or parallel to the axis of the apparatus.

The vanes may be made of any material capable of resisting dimensionaldistortion under the loads experienced in operation and which arefurther safe in operation. Thus mild steel and fibrereinforced plasticsare suitable materials.

With reference to the process aspects of the invention, we find that theparticulate matter is preferably supplied at as high a concentration inas small a quantity of air as is feasible for this reason a turbobloweris preferred to a centrifugal fan as the fluid supply means.

Fluid, for example air, supplied at presures of up to 0.35 Kgcm" arepreferred, more preferably pressures between 0.05 and 0.2 Kg.cm andfluid flow rates of about 0.02 to 0.05 m. s are preferable.

The fluid should be supplied in a turbulent state, as opposed to astreamlined flow. Whilst there will be inequalities in the degree ofturbulence, for example towards the edge of the ducting, it is anessential feature of our invention that turbulent conditions aremaintained so that the particulate matter remains suspended in thestream of fluid. This is particularly important just before thesuspended particles are deposited on the substrate.

A substantially uniform supply of particulate matter should be fed intothe stream of turbulent fluid. We find with flock fibres of a -cellulosethat a conventional vibro-screw feeder is a convenient and satisfactorymeans of ensuring a uniform supply to the turboblower, the rate ofsupply being readily adjustable by adjustment of the speed of rotationof the screw. The uniformity of supply of particulate matter may beimproved by placing a vibrated gauze between the screw feed and thepoint at which the particulate matter enters the stream of gaseousfluid.

By rotating the second member within the first member there ismaintained a turbulency in the suspension of flock in air which preventsany localised concentration of particulate matter and the sweepingaction of the vanes prevents any deposition of particulate matter on theinner walls of the first member.

We find that when the suspension of particulate matter in gaseous fluidis supplied to one end only of the hollow shaft of the second member,the apparatus of the invention is capable of uniform distribution acrosswidths of up to about 2 metres. For greater widths it is preferable tosupply the shaft with a suspension of particulate matter in gaseousfluid from both ends in which case it is desirable that the opposingstreams are directed by baffles or otherwise, so that the one streampasses over or alongside the other, so that a direct meeting of theopposing streams to the centre of the second member is avoided. Thenature of the particulate matter and the substrate will obviously dependupon the type of product it is desired to make.

The invention is further illustrated in the following drawing in whichFIG. 1 shows the construction of the first and second member inperspective from below, the second member being partly withdrawn fromthe first member,

FIG. 2 is a cross-section through the assembled first and second member,

FIG. 3 is a schematic side view of the apparatus of the invention, and,

FIG. 4 illustrates the use of the invention in the manufacture of anon-woven fabric.

Referring to FIGS. 1 and 2, reference number 1 indicates the firstmember and reference number 2 the second member. First member 1 consistsof a hollow tubular casing 3 having a longitudinally extending narrowslot 4. Second member 2 comprises vanes 7 which are supported at theirends by support means (not shown in FIGS. 1 and 2 for clarity), saidsupport means being linked by means of axial shaft 5. Bracing members 6link adjacent vanes 7, to further support vanes 7 and thereby to improvethe stability second member 2. Vanes 7 extend outwardly radially and arearranged so 4 that a small clearance exists between the tips of vanes 7and the inner wall of easing 3 (shown in FIG. 2);

Vanes 7 and bracing means 6 define a central channel 20 (shown in FIG.2) which extends the length of second member 2. Means (not shown) tosupply particulate matter suspended in gaseous fluid to channel 20 areincorporated in at least one of the support means.

The support means (not shown) are provided with rotatable bearings (notshown) and drive means (not shown) whereby second member 2 may berotated.

As shown in FIG. 2 the assembled first and second members 1, 2 aresupported by rigid stands 10 shown in the vicinity of advancingsubstrate 11.

FIG. 3 shows schematically first member 1, stands 10, support means 8 ofthe second member, means 9 whereby particulate matter is supplied to theapparatus and thence to substrate 11. Reference numeral 12 indicates aturbo-blower, which is connected by vibroscrew feed 13 to storage hopper14. If the length of the apparatus of the invention is long, supplymeans 9, turbo-blower l2, vibro-screw feed 13 and hopper 14 may beduplicated at the other end of the apparatus as indicated in dottedlines. Alternatively a single screw feed 13 may feed both ends of theapparatus.

In operation, particulate material stored in hopper 14 is metered byvibro-screw feed 13 to turbo-blower 12 and thence into central channel20 of second member 2 by way of supply means 9. Second member 2 isrotated by, for instance, an electric motor and drive means (not shown).The air-borne particulate matter passes from channel 20 into the volumesbetween vanes 7 and the inner surface of casing 3, and thence via slot 4onto advancing substrate 11.

The invention is further illustrated by the following example withreference to FIG. 4, in which one application of the invention isdescribed.

EXAMPLE A non-woven web having a weight of 12 gm and composed ofcontinuous bicomponent filaments having an extensibility to break ofabout and a count of about 5 denier per filament, the components being acore of nylon 6.6 with a sheath of nylon 6 (the core weighing about 65%of the total filament weight) was manufactured by forwarding the freshlyspun filaments onto a collecting surface by means of a traversingpneumatic forwarding device. The web so produced, which had a width of1.0 m, was wound up on a roll, interleaved with tissue paper, and theroll was subsequently passed through an atmosphere of steam at 1.75Kg.cm at a speed giving a residence time of some 5 secs, which treatmentbonded the filaments of the web together by softening the nylon 6sheath. The bonded web was rewound as a roll, the interleaving tissuepaper being discarded. This roll of web was used as the feed stock forthe apparatus illustrated in FIG. 4, reference numeral 20 indicating theroll of web, and reference numeral 21 the passage of the web as it wasunwound from roll 20.

Base web 21 was passed between nip rolls 22, 23 at a speed of about 5 m.min roll 22 being a gravure roll contacting adhesive 25 contained inbath 26. Doctor blade 24 ensures even distribution of adhesive along thelength of roll 22 and hence across the width of web 21. The adhesiveemployed was a self-linking acrylic copolymer, designated Primal HA8,supplied by Lennig Chemicals Limited, emulsified in water to give about50% solids. The amount of solids applied to the web 21 by roll 22 wasadjusted to about 2 g. m by further diluting the emulsion with water.

The base web coated with adhesive (designated 27) was advanced to aflocking station 28, comprising the apparatus of the present inventionsituated above (29) and below (30) web 27. Flock fibres of a-cellulosehaving a nominal length of 0.3 cm were advanced from storage hoppers(not shown) via vibro-screw feeds 31, 31' into a stream of air atventuri 32, 32, said stream of air being supplied by turbo-blowers 33,33 at a rate of 50 ft /min. The air-borne flock fibres, which weresupplied at a rate of 100 g. min were passed via pipe 9, 9' (shownschematically) to barrel 5,5 and was distributed uniformly by rotatingvanes 7, 7' onto the adhesive coated base web 27 via slot 4, 4'. Slot 4was offset from slot 4'. The apparatus 29 and 30 comprised a cylindricalfirst member of length 110 cm and diameter 15.5 cm having a slot ofwidth 0.65 cm. The second 7 member in each case comprised 18 equispacedvanes mounted radially with respect to the axis. The vanes weremanufactured from mild steel sheet of 1.50 mm thickness and weresupported by mild steel sheet bracing means spaced apart at 2.5 cmintervals. The second member was rotated at 385 rpm. The clearancebetween the vanes and the inner wall of the second member was nominally0.6 cm. The apparatus 29, 30 was enclosed within extraction hood 35, 35and mild suction was applied to remove any surplus flock fibres whichfailed to contact the adhesive. The flock fibres were thereby applied tothe base web at a rate which gave 20 cm flock fibres on the web.Subsequently, flocked web was passed through a hot dry zone 41 in whichthe adhesive was cured. The zone 41 may be a hot air blower, radiantheaters or a hot air oven. The residence time was about 2 minutes at atemperature of 140C. Finally web 40 is passed via idler and spreadingrollers 45, 46 to wind-up means 50.

The physical properties of the product were found to be as follows:

Weight: Tear strength:

Machine direction: 1.95 Kg Cross-machine direction: 2.l0 Kg Machinedirection: 42.0% Cross-machine direction: 430 g.cm

Machine direction: 1.40 Kg Cross-machine direction: l.27 Kg Extension:

Burst strength: Breaking load:

The product was a lightweight drapeable fabric having good tearstrength, burst strength and breaking load. It had excellent drape,stretch properties and crease resistance. It could be dyed, printed, cutwithout fraying,v sewn, glued and sterilised by conventional 1.Apparatus for the uniform distribution of particulate matter on to asubstrate advancing at a uniform rate, comprising an elongated hollowcylinder provided with a slot extending along its effective length; amember located coaxially within the cylinder and rotatable about itslengthwise axis, said member comprising support means extending beyondthe ends of said hollow cylinder and having mounted therebetween aplurality of vanes disposed within said hollow cylinder, each of saidvanes extending along the entire effective length of said hollowcylinder, the outer edges of said vanes being adjacent but not touchingthe inner wall of said cylinder, said vanes having radially measureddimensions less than the internal radius of the hollow cylinder todefine a central, cylindrical channel within said member; means forsupplying particulate matter suspended in a turbulent stream of gaseousfluid at a constant rate to said channel defined within said member;means for axially rotating said member at a uniform rate; and means foradvancing a substrate perpendicular to said slot in said hollowcylinder, the slot in said hollow cylinder and said rotatable membereach having a length sufficient to enable uniform distribution ofparticulate matter onto a substrate having a width in the range of 1meter and above.

2. Apparatus according to claim 1, wherein bracing means extendingbetween adjacent vanes are provided at intervals along the length of thesaid member.

3. Apparatus according to claim 2, wherein said bracing means are set atangles to planes perpendicular to the lengthwise axis of said member.

4. Apparatus according to claim 2, wherein said bracing means are setperpendicularly to the lengthwise axis of said second member and atintervals of between 2 and 8 cm.

5. Apparatus according to claim 1, wherein there are at least 6 vanespreferably not less than 16 vanes in said member.

6. Apparatus according to claim 1, wherein an axial shaft is situatedwithin central channel of said second member links the vane supportmeans thereof.

7. Apparatus according to claim 1, wherein the crosssection of the vanesis wedge-shaped.

8. Apparatus according to claim 1, wherein the vanes are manufactured ofmild steel.

9. Apparatus according to claim 1, wherein the vanes are manufactured ofa fibre-reinforced plastic material.

10. Apparatus according to claim 1, wherein the means for supplyingparticulate matter comprises a hopper and a vibrated screw feed.

1 1. Apparatus according to claim 1, wherein the gaseous fluid issupplied by means of a turbo-blower.

1. Apparatus for the uniform distribution of particulate matter on to asubstrate advancing at a uniform rate, comprising an elongated hollowcylinder provided with a slot extending along its effective length; amember located coaxially within the cylinder and rotatable about itslengthwise axis, said member comprising support means extending beyondthe ends of said hollow cylinder and having mounted therebetween aplurality of vanes disposed within said hollow cylinder, each of saidvanes extending along the entire effective length of said hollowcylinder, the outer edges of said vanes being adjacent but not touchingthe inner wall of said cylinder, said vanes having radially measureddimensions less than the internal radius of the hollow cylinder todefine a central, cylindrical channel within said member; means forsupplying particulate matter suspended in a turbulent stream of gaseousfluid at a constant rate to said channel defined within said member;means for axially rotating said member at a uniform rate; and means foradvancing a substrate perpendicular to said slot in said hollowcylinder, the slot in said hollow cylinder and said rotatable membereach having a length sufficient to enable uniform distributioN ofparticulate matter onto a substrate having a width in the range of 1meter and above.
 2. Apparatus according to claim 1, wherein bracingmeans extending between adjacent vanes are provided at intervals alongthe length of the said member.
 3. Apparatus according to claim 2,wherein said bracing means are set at angles to planes perpendicular tothe lengthwise axis of said member.
 4. Apparatus according to claim 2,wherein said bracing means are set perpendicularly to the lengthwiseaxis of said second member and at intervals of between 2 and 8 cm. 5.Apparatus according to claim 1, wherein there are at least 6 vanespreferably not less than 16 vanes in said member.
 6. Apparatus accordingto claim 1, wherein an axial shaft is situated within central channel ofsaid second member links the vane support means thereof.
 7. Apparatusaccording to claim 1, wherein the cross-section of the vanes iswedge-shaped.
 8. Apparatus according to claim 1, wherein the vanes aremanufactured of mild steel.
 9. Apparatus according to claim 1, whereinthe vanes are manufactured of a fibre-reinforced plastic material. 10.Apparatus according to claim 1, wherein the means for supplyingparticulate matter comprises a hopper and a vibrated screw feed. 11.Apparatus according to claim 1, wherein the gaseous fluid is supplied bymeans of a turbo-blower.
 12. Apparatus according to claim 10, wherein avibrated gauze is interposed between the screw feed and the point atwhich the particulate matter enters the stream of gaseous fluid. 13.Apparatus according to claim 1, wherein the suspension of particulatematter is directed into the central chamber within the said secondmember from both ends thereof.